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DAVID POWERS
In this book you’ll learn how to:
Produce code that’s easier to maintain by adopting OOP techniques.
Use best practices by implementing basic design patterns.
Simplify complex code through encapsulation.
Unlock the secrets of the Standard PHP Library.
Generate your own news feed using Really Simple Syndication (RSS).
P
HP is easy to learn and a great way to add dynamic
functionality to web sites, such as sending email from
online forms and generating database-driven content.
But there soon comes a time when you realize you’re
writing similar scripts over and over again. By adopting
an object-oriented approach, you can avoid the need to
reinvent the wheel every time, creating scripts that are
reusable, easier to understand, and easier to maintain.
The main barrier to object-oriented programming (OOP)
is that it’s based on unfamiliar concepts, such as objects,
classes, interfaces, encapsulation, and polymorphism.
This book strips away the mystique and explains each
concept in an approachable and understandable way. It
provides a gentle but fast-paced introduction to OOP
as it applies to PHP. Another barrier to the adoption of
OOP among PHP developers has been the slow migra-
tion from PHP 4, which used a radically different—and
inferior—object model. Now that PHP 4 has come to the
official end of its life, this book concentrates exclusively
on using OOP with PHP 5 and 6. So you can be confi-
dent that you’re learning skills that won’t be out of date

almost as soon as you put the book down.
Through a series of practical projects, this book shows
how OOP can be used to group related functions in a
portable manner. The projects include a validator for fil-
tering user input, a class that avoids the need to remember
all the esoteric PHP date formatting codes, and an XML
generator—everyday requirements for a lot of develop-
ers. Although the emphasis is on learning how the code
works, if you’re in a hurry, the PHP classes used in the
book can be downloaded from the friends of ED web
site and incorporated into existing sites with a minimum
of effort.
The book is aimed at intermediate developers with a good
understanding of PHP basics, such as variables, arrays,
functions, loops, and conditional statements. It provides
the necessary groundwork for advancing on to using an
object-oriented framework, such as the Zend Framework,
and taking your PHP coding skills to the next level.
Powers
CYAN YELLOW
MAGENTA BLACK
PHP OBJECT-ORIENTED SOLUTIONS
Understand basic OOP concepts,
such as inheritance, encapsulation,
and polymorphism.
Extend core PHP classes.
Design and create your own classes
for PHP 5 and 6.
Also Available
US $36.99

Mac/PC compatible
www.friendsofed.com
/>SHELVI NG CATE GOR Y
1. PHP
Available from Apress
ISBN 978-1-4302-1011-5
9 781430 210115
5 3 6 9 9

PHP Object-Oriented
Solutions
David Powers
10115fm.qxd 7/22/08 12:10 PM Page i
PHP Object-Oriented Solutions
Copyright © 2008 by David Powers
A
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Credits
Lead Editor
Ben Renow-Clarke
Technical Reviewer
Seungyeob Choi
Editorial Board
Clay Andres, Steve Anglin, Ewan Buckingham,
Tony Campbell, Gary Cornell, Jonathan Gennick,
Matthew Moodie, Joseph Ottinger, Jeffrey Pepper,
Frank
P

ohlmann, Ben R
enow-Clarke, Dominic Shakeshaft
,
Matt Wade, Tom Welsh
Project Manager
Beth Christmas
Copy Editors
Heather Lang and Damon Larson
Associate Production Director
Kari Brooks-Copony
Production Editor
Laura Esterman
Compositor
Molly Sharp
Proofreader
Patrick Vincent
Indexer
Toma Mulligan
Artist
April Milne
Interior and Cover Designer
Kurt Krames
Manufacturing Director
Tom Debolski
10115fm.qxd 7/22/08 12:10 PM Page ii
CONTENTS AT A GLANCE
About the Author
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
xi
About the Technical Reviewer

. . . . . . . . . . . . . . . . . . . . . . . . . . . .
xiii
Acknowledgments
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
xv
Introduction
.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
xvii
Chapter 1: Why Object-Oriented PHP?
. . . . . . . . . . . . . . . . . . . . . . .
3
Chapter 2: Writing PHP Classes
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
23
Chapter 3: Taking the Pain Out of Working with Dates
. . . . . . . .
77
Chapter 4: Using PHP Filters to Validate User Input
. . . . . . . . . .
121
Chapter 5: Building a Versatile Remote File Connector
. . . . . . .
169
Chapter 6: SimpleXML—Couldn’t Be Simpler
. . . . . . . . . . . . . . .
207
Chapter 7: Supercharged Looping with SPL
.
. . . . . . . . . . . . . . . .

251
Chapter 8: Generating XML from a Database
. . . . . . . . . . . . . . .
289
Chapter 9: Case Study: Creating Your Own RSS Feed
. . . . . . . . .
321
Index
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
355
10115fm.qxd 7/22/08 12:10 PM Page iii
10115fm.qxd 7/22/08 12:10 PM Page iv
CONTENTS
About the Author
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
xi
About the Technical Reviewer
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
xiii
Acknowledgments
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
xv
Introduction
.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
xvii
Chapter 1: Why Object-Oriented PHP?
. . . . . . . . . . . . . . . . . . . . . . .
3
Understanding basic OOP concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

How OOP evolved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Using classes and objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Protecting data integrity with encapsulation. . . . . . . . . . . . . . . . . . . . . . . . . 8
Polymorphism is the name of the game .
.
.
. . . . . . . . . . . . . . . . . . . . . . . 10
Extending classes through inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Deciding on a class hierarchy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Using best practice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
How OOP has evolved in PHP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
OOP since PHP 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Preparing for PHP 6
.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Choosing the right tools to work with PHP classes . . . . . . . . . . . . . . . . . . . . . . . 16
Using a specialized script editor
.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Chapter review. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Chapter 2: Writing PHP Classes
.
.
.
. . . . . . . . . . . . . . . . . . . . . . . . .
23
Formatting code for readability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Using the Zend Framework PHP Coding Standard .
. . . . . . . . . . . . . . . . . . . . 25
Choosing descriptive names for clarity . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Creating classes and objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Defining a class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Controlling access to properties and methods
.
.
. . . . . . . . . . . . . . . . . . . . . 27
Quick review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Setting default values with a constructor method . . . . . . . . . . . . . . . . . . . . . 33
v
10115fm.qxd 7/22/08 12:10 PM Page v
Using inheritance to extend a class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
D
efining a child class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
A
ccessing a parent class’s methods and properties . . . . . . . . . . . . . . . . . . . . 39
Using the scope resolution operator . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Controlling changes to methods and properties . . . . . . . . . . . . . . . . . . . . . . 44
Preventing a class or method from being overridden. . . . . . . . . . . . . . . . . 44
Using class constants for properties . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Creating static properties and methods . . . . . . . . . . . . . . . . . . . . . . . . 47
Quick review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Loading classes automatically. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Exploring advanced OOP features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Creating abstract classes and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Simulating multiple inheritance with interfaces . . . . . . . . . . . . . . . . . . . . . . 54
Understanding which class an object is an instance of . . . . . . . . . . . . . . . . . . 55
Restricting acceptable data with type hinting . . . . . . . . . . . . . . . . . . . . . 56
Using magic methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Converting an object to a string . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Cloning an object . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Accessing properties automatically . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Accessing methods automatically . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Cleaning up with a destructor method . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Handling errors with exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Throwing an exception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Catching an exception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Extracting information from an exception . . . . . . . . . . . . . . . . . . . . . . . . . 68
Extending the Exception class .
.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Using comments to generate code hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Writing PHPDoc comments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Chapter review. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Chapter 3: Taking the Pain Out of Working with Dates
.
.
.
. . . . .
77
Designing the class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Examining the built-in date-related classes . . . . . . . . . . . . . . . . . . . . . . . . . 79
Using the DateTime class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Setting the default time zone in PHP . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Examining the DateTimeZone class . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Using the DateTimeZone class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Deciding how to extend the existing classes . . . . . . . . . . . . . . . . . . . . . . . . 89
Building the class
.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Creating the class file and constructor . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

R
esetting the time and date .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Accepting dates in common formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Accepting a date in MM/DD/YYYY format . . . . . . . . . . . . . . . . . . . . . . . 98
Accepting a date in DD/MM/YYYY format . . . . . . . . . . . . . . . . . . . . . . . 99
Accepting a date in MySQL format
.
.
. . . . . . . . . . . . . . . . . . . . . . . . . 99
Outputting dates in common formats
. . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Outputting date parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Performing date-related calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
CONTENTS
vi
10115fm.qxd 7/22/08 12:10 PM Page vi
Adding and subtracting days or weeks . . . . . . . . . . . . . . . . . . . . . . . . 105
A
dding months . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
S
ubtracting months . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Adding and subtracting years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
Calculating the number of days between two dates . . . . . . . . . . . . . . . . . 113
Creating a default date format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
Creating read-only properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Organizing and commenting the class file . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
Chapter review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Chapter 4: Using PHP Filters to Validate User Input
. . . . . . . . . .

121
Validating input with the filter functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
Understanding how the filter functions work . . . . . . . . . . . . . . . . . . . . . . . 123
filter_has_var() . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
filter_list() . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
filter_id(). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
Setting filter options.
.
.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
Filtering single variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
Setting flags and options when filtering a single variable . . . . . . . . . . . . . . 134
Filtering multiple variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
Setting a default filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Building the validation class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
Deciding what the class will do. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
Planning how the class will work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
Coding the validation class properties and methods . . . . . . . . . . . . . . . . . . . 140
Naming properties and defining the constructor .
.
. . . . . . . . . . . . . . . . 140
Setting the input type and checking required fields . . . . . . . . . . . . . . . . . 142
Preventing duplicate filters from being applied to a field . . . . . . . . . . . . . . 147
Creating the validation methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
Creating the methods to process the tests and get the results . . . . . . . . . . . 157
Using the validation class .
.
.
.
.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Sticking to your design decisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
Chapter review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
Chapter 5: Building a Versatile Remote File Connector
. . . . . . .
169
Designing the class .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
Building the class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
Defining the constructor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
Checking the URL
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
Retrieving the remote file. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
Defining the accessDirect() method
.
. . . . . . . . . . . . . . . . . . . . . . . . . 180
Using cURL to retrieve the remote file . . . . . . . . . . . . . . . . . . . . . . . . 186
Using a socket connection to retrieve the remote file. . . . . . . . . . . . . . . . 190
Handling the response headers from a socket connection . . . . . . . . . . . . . 196
Generating error messages based on the status code
.
.
. . . . . . . . . . . . . . 202
Final testing
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
Ideas for improving the class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
Chapter review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
CONTENTS
vii
10115fm.qxd 7/22/08 12:10 PM Page vii

Chapter 6: SimpleXML—Couldn’t Be Simpler
.
. . . . . . . . . . . . . .
207
A quick XML primer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
W
hat is XML?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
How XML documents are structured. . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
The rules of writing XML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
Using HTML entities in XML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
Inserting HTML and other code in XML . . . . . . . . . . . . . . . . . . . . . . . . 213
Using SimpleXML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
Loading an XML document with SimpleXML . . . . . . . . . . . . . . . . . . . . . . . 217
Loading XML from a file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
Loading XML from a string . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
Extracting data with SimpleXML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
Accessing text nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
Accessing attributes .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
Accessing unknown nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
Saving and modifying XML with SimpleXML . . . . . . . . . . . . . . . . . . . . . . . . . . 228
Outputting and saving SimpleXMLElement objects. . . . . . . . . . . . . . . . . . . . 228
Modifying SimpleXMLElement objects. . . . . . . . . . . . . . . . . . . . . . . . . . . 231
Changing the values of text and attributes . . . . . . . . . . . . . . . . . . . . . . 231
Removing nodes and values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
Adding attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
Adding new elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
Using SimpleXML with namespaces .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
How namespaces are used in XML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

Handling namespace prefixes in SimpleXML . . . . . . . . . . . . . . . . . . . . . . . 236
Handling namespaced attributes. . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
Finding out which namespaces a document uses. . . . . . . . . . . . . . . . . . . . . 242
Using SimpleXML with XPath .
.
.
.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
A quick introduction to XPath . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
Using XPath to drill down into XML . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
Using XPath expressions for finer control. . . . . . . . . . . . . . . . . . . . . . . 246
Using XPath with namespaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
Registering namespaces to work with XPath . . . . . . . . . . . . . . . . . . . . . 247
Chapter review .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
Chapter 7: Supercharged Looping with SPL
.
. . . . . . . . . . . . . . . .
251
Introducing iterators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
Using an array with SPL iterators
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
Limiting the number of loops with the LimitIterator . . . . . . . . . . . . . . . . . . . 253
Using SimpleXML with an iterator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
Setting options for R
egexIterator .
. . . . . . . . . . . . . . . . . . . . . . . . . . 259
Looping sequentially through more than one set of data . . . . . . . . . . . . . . . . 263
Looking ahead with the CachingIterator. . . . . . . . . . . . . . . . . . . . . . . . . . 265

Using anonymous iterators as shorthand . . . . . . . . . . . . . . . . . . . . . . . . . 268
Examining files and directories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
Using DirectoryIterator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270
Including subdirectories in a single operation
.
.
.
. . . . . . . . . . . . . . . . . . . 271
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Extracting file information with SplFileInfo . . . . . . . . . . . . . . . . . . . . . . . . 273
F
inding files of a particular type . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
R
eading and writing files with SplFileObject . . . . . . . . . . . . . . . . . . . . . . . 275
Extending iterators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281
Understanding the Iterator interface . . . . . . . . . . . . . . . . . . . . . . . . . . . 282
Extending the FilterIterator class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
Chapter review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
Chapter 8: Generating XML from a Database
. . . . . . . . . . . . . . .
289
Designing the application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
Defining the application’s purpose. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
Setting the requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
Building the application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
Creating the database connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
Getting the database result . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
Defining the properties and constructor . . . . . . . . . . . . . . . . . . . . . . . 295

Implementing the Iterator interface .
.
.
. . . . . . . . . . . . . . . . . . . . . . . 296
Implementing the Countable interface . . . . . . . . . . . . . . . . . . . . . . . . 298
Generating the XML output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
Defining the properties and constructor . . . . . . . . . . . . . . . . . . . . . . . 303
Setting the SQL query. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305
Setting the root and top-level node names. . . . . . . . . . . . . . . . . . . . . . 305
Obtaining the primary key . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
Setting output file options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
Using XMLWriter to generate the output . . . . . . . . . . . . . . . . . . . . . . . 307
Chapter review .
.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
Chapter 9: Case Study: Creating Your Own RSS Feed
. . . . . . . . .
321
Understanding the RSS 2.0 format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
The structure of an RSS 2.0 feed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
What the <channel> element contains .
.
.
.
.
. . . . . . . . . . . . . . . . . . . 323
What the <item> elements contain . . . . . . . . . . . . . . . . . . . . . . . . . . 325
Deciding what the feed will contain . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
Building the class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
Populating the elements that describe the feed . . . . . . . . . . . . . . . . . . . . . 328

P
opulating the <item> elements
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
Building the SQL query . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
Creating the <pubDate> element . . . . . . . . . . . . . . . . . . . . . . . . . . . 338
Creating the <link> elements
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
Creating helper methods to format <item> child elements. . . . . . . . . . . . . 344
Generating the XML for the <item> elements
.
. . . . . . . . . . . . . . . . . . . 346
Where to go from here . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352
Index
.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
355
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